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Definition from buildingSMART International: An IfcClassificationReference is a reference into a classification system or source (see IfcClassification). An optional inherited ItemReference key is also provided to allow more specific references to classification items (or tables) by type. The inherited Name attribute allows for a human interpretable designation of a classification notation (or code) - see use definition of "Lightweight Classification".

HISTORY: New entity in IFC 2x.

Use Definitions

Lightweight Classification

The IfcClassificationReference can be used as a form of 'lightweight' classification through the 'ItemReference' attribute inherited from the abstract IfcExternalReference class. In this case, the 'ItemReference' could take (for instance) the Uniclass notation "L6814" which, if the classification was well understood by all parties and was known to be taken from a particular classification source, would be sufficient. The Name attribute could be the title "Tanking". This would remove the need for the overhead of the more complete classification structure of the model.

However, it is not recommended that this lightweight method be used in cases where more than one classification system is in use or where there may be uncertainty as to the origin or meaning of the classification.

Referencing from an External Source

Classifications of an object may be referenced from an external source rather than being contained within the IFC model. This is done through the IfcClassificationReference class.

EXPRESS specification:

ENTITY IfcClassificationReference
SUBTYPE OF ( IfcExternalReference);
ReferencedSource  :  OPTIONAL IfcClassification;

Attribute definitions:

ReferencedSource  :  The classification system or source that is referenced.

Inheritance graph

ENTITY IfcClassificationReference;
ENTITY IfcExternalReference;
Location  :  OPTIONAL IfcLabel;
ItemReference  :  OPTIONAL IfcIdentifier;
Name  :  OPTIONAL IfcLabel;
ENTITY IfcClassificationReference;
ReferencedSource  :  OPTIONAL IfcClassification;